1. Field of the Invention
The present invention relates to a dual band portable phone, and more particularly to a technique for quickly switching from one mobile phone system to another and a method for the same.
2. Description of the Related Art
A PHS (personal handyphone system) is known as a mobile phone system, and employs a cellular technology in which an area size; where electromagnetic wave can be received is up to about 100 meters radially from the base station of each cell. Therefore, it is essential to provide many base stations for a wide service area. While the PHS system is less in service fee than any other mobile phone systems, it is sometimes difficult to receive the electromagnetic wave.
A GSM (global system for mobile communications) uses a larger sized cellular area which is relatively large and hardly concerns the above disadvantage. The GSM system is however higher in the service fee than the PHS system.
To eliminate such disadvantage, a dual band portable phone operable in both the PHS system and the GSM system has been developed. The dual band portable phone usually operates in the PHS mode. When being moved out of the service area for the PHS mode, the portable phone starts operating using the GSM mode. It is now defined that the PHS mode is almode where the dual band portable phone is used as a mobile station of the PHS system and the GSM mode is a mode where the same is used as a mobile station of the GSM system.
When the dual band portable phone is turned on, it starts a function for searching the control channel in either the PHS system or the GSM system. In the PHS system, the channel number (frequency) of the control channel is assigned to each dual band portable phone by a service supplier (an. operator) of the PHS system. The dual band portable phone has a built-in memory in which the channel number is registered such that the control channel of the PHS system can be quickly found.
In the GSM system, the channel number of the control channel may arbitrarily be determined by its operator when desired. This requires the dual band portable phone to search a desired control channel through checking all the available channels for registration of the position. When the dual band portable phone is moved from the service area of the PHS system to the service area of the GSM system, it has to search all the available channels to determine the control channel to be used during the searching action.
A related technology is disclosed as xe2x80x9cmethod of registering the position in mobile radio communicationxe2x80x9d in Japanese Laid Open Patent Application (JP-A-Showa 63-203025). The method of registering the position in mobile radio communication involves registering the position of a mobile portable phone when it is moved from one cell to another in the mobile phone system. More particularly, while a single control channel is used commonly in different systems, both automatic position registration and manual position registration are enabled. However, in the Japanese Laid Open Patent Application (JP-A-Showa 63-203025), no technique is disclosed for allowing the mobile portable phone to move between the service areas of different mobile phone systems.
Also, xe2x80x9cradio communications apparatus and method of radio communicationsxe2x80x9d is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 9-51321). The reference describes a technology for allocating frequency bands to two communication systems (for CDMA and cordless telephone). However, a technique is not indicated to quickly perform a position registering process when the portable phone is moved between the service areas of the. different mobile phone systems.
Moreover, xe2x80x9cCMTS/MCS compatible mobile portable phonexe2x80x9d is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-102923). The CMTS/MCS compatible mobile portable phone operates in either of a CMTS mode and an MCS mode when it is turned on. However, the CMTS/MCS compatible mobile portable phone cannot switch from its dedicated mobile phone system to another mobile phone system when it is moved out of the service area of the dedicated mobile phone system and its communication is disabled.
An object of the present invention is to eliminate the foregoing disadvantages of conventional mobile telephones.
Another object is to provide a dual band portable phone capable of quickly performing a position registering process for another mobile phone system when the portable phone is moved out of a service area of the current mobile phone system.
Still another object of the present invention is to provide a method of switching between different mobile phone systems.
In order to achieve an aspect of the present invention, a dual band portable phone includes a first mobile phone system used in a first mode, a second mobile phone system used in a second mode, a storing section and a control section. The storing section has a mode area for storing a mode data indicative of a current operation mode, a first area for storing a first control channel data indicative of a first control channel used for the first mobile phone system in the first mode, and a second area for storing a second control channel data indicative of a second control channel used for the second mobile phone system in the second mode. The mode data indicates the first mode at present. The control section performs a position registration of the portable phone using the second control channel data stored in the storing section to set the second mode, when a first radio communication using the first mobile phone system becomes impossible while the first radio communication is performed in the first mode. The control section also performs a second radio communication using the second mobile phone system.
The control section may perform the position registration of the portable phone using the second control channel data stored in the storing section to set the second mode, when the portable phone is moved out of a first service area of the first mobile phone system while the first radio communication is performed in the first mode.
Also, the control section may transmit a position registration request to a station for the second mobile phone system using the second control channel data, and may set the mode data indicative of the second mode in the storing section in response to a position registration completion notice from the station to set the second mode.
In addition, the control section may perform a position registration of the portable phone using the first control channel data stored in the storing section in response to a mode change request while the second radio communication is performed in the second mode, set the first mode in response to the position registration of the portable phone using the first control channel data, and perform a radio communication using the first mobile phone system. In this case, the mode change request may be issued when the portable phone is moved out of a service area of the second mobile phone system and into a service area of the first mobile phone system. Instead, the mode change request may be issued when the portable phone is located in a service area of the second mobile phone system and is moved into a service area of the first mobile phone system. Otherwise, the mode change request may be issued when the portable phone is located in a service area of the first mobile phone system and an operation unit is operated.
It is preferable that the control section acquires the first control channel data and the second control channel data in response to a start request, to store in the storing section. In this case, the start request may be issued when a power supply of the portable phone is turned on. Also, the control section sets the mode data indicative of the first mode in the storing section when both of the first control channel data and the second control channel data are acquired or when the first control channel data is acquired. Thus, the control section sets the mode data indicative of the second mode in the storing section when the second control channel data is acquired and when the first control channel data is not acquired.
In addition, the control section selects one having the highest reception electric field intensity level from among control channels for each of the first and second mobile phone systems to store a data corresponding to the one having the highest reception electric field intensity level in the storing section.
In the above, it is preferable that the first mobile phone system is a PHS system and a second mobile phone system is a GSM system.
In order to achieve another aspect of the present invention, a method of performing communication in a dual band portable phone includes:
performing communication using a first mobile phone system in a first mode, a position registration having been performed using the first mobile phone system based on a first control channel data indicative of a first channel predetermined;
switching from the first mobile phone system to a second mobile phone system using a second control channel data indicative of a second channel predetermined such that a second mode is set; and
continuing the communication using the second mobile phone system in the second mode.